Dynamics of the formation of mixed alkanethiol monolayers: Applications in structuring biointerfacial arrangements

The central of molecular recognition at interfaces is of importance in many areas of bioelectronics and biocatalysis, particularly in the design of biosensors, where it may be desirable to be able to manipulate the degree of interaction between a protein and a metal surface. To develop appropriate models to study such phenomena, we have produced mixed monolayers on gold by the displacement of molecules from a previously formed, homogeneous self-assembled monolayer (SAM) of an alkanethiol (mercaptoethylamine) using a solution containing a thiol with a different functional headgroup (mercaptopropanol). The dynamics of the formation of the resultant surfaces were investigated using high-resolution X-ray photoelectron spectroscopy (XPS) to probe both the C(1s) and N(1s) environments, corresponding to the different species in the SAMs. To illustrate the application of such interfacial arrangements and to further understand their role in controlling protein-surface interactions, two systems were investigated: in the first instance, the electron transfer between the small redox protein, cytochrome c, and the mixed monolayers was investigated using cyclic voltammetry; second, the potential for producing surfaces with different amounts of immobilized antibodies was demonstrated using fluorescence microscopy.